Improving performance for huge files with XSLT

Hi,
I'm using XSLT to convert xml files into other xml files. I have to
convert huge xml files (containing, e.g. 50000/100000 nodes), but the
perfomance is becoming a real problem: it takes more or less 20 minutes
to convert a file with 100000 nodes.
Are there some general methods to improve the performance with huge xml
files? Did somebody encounter the same problem? How did you solve it?
Thanks,
Ornella Piva
XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list